Pneumatic tube carrier systems are a well-known means for the automated transport of materials between a multitude of user stations, any of which may be the origination location or destination location of a transport carrier. A typical system includes a number of pneumatic tubes interconnected in a network to transport carriers between various user stations. Various blowers and transfer units provide the force and path control means, respectively, for moving the carriers through and from tube-to-tube within the system.
Arrangement of the pneumatic tubes that connect the various locations may be in any manner that allows transfer of the carriers between various stations. Generally, a single pneumatic tube interconnects an individual station to the network. In this arrangement, such the single pneumatic tube transfers carriers to and from the station. Dedicated pneumatic tubes may connect other portions of the network. Complex pneumatic tube carrier systems may include scores or even hundreds of user stations.
Directing traffic in a pneumatic tube carrier system is a system control center (SCC). An SCC may determine carrier paths, or routes, through a system. In some instances, the SCC may dynamically alter carrier paths to avoid gridlock conditions. Current systems largely base routing determinations upon “predictions”, or inferences, as to where each carrier “should be” within a system given the times/locations of entry and intended transport paths of all carriers concurrently handled by the system.
Occasionally, a system may misdirect a given carrier because of equipment error. Alternatively, a system may misdirect numerous carriers because of the presence of a “floater” carrier (e.g., an unidentified carrier) within a system. The presence of even a single, unaccounted for carrier may severely undermine the accuracy of a number of prediction-based determinations made by an SCC, thereby adversely impacting the handling of numerous carriers. This may require purging the system to remove all carriers from the components of the system.
In other instances, the system may shut down (i.e., partially or totally) after a disturbance to the normal operation of the system or carrier movement within the system. Examples of such disturbances include Urgent Off situations and temporary power loss by the SCC. Such situations may leave one or more carriers stranded within the system. Accordingly, it may be necessary to purge the system to recover any stranded carriers.
Purging a pneumatic system has typically entailed the sequential operation of each pneumatic component in the system for a period sufficient to ensure that, if a pneumatic component held a stranded carrier, the carrier passes to a subsequent component. Eventually, all stranded carriers exit the system, typically at a user station. However, delivery of the stranded carriers may not be to a correct user station. Further, such sequential purging is time consuming, often requiring an hour or more for a modest sized hospital system.